E0089: immutable_write

E0089 immutable_write — an overwrite or delete on an [immutable] slot.

A compile-time error of soma check, the checker of the Soma programming language (soma explain E0089).

The rule

An [immutable] slot is append-only: an entry never changes once written, so .delete (or an overwrite) on it can only fail at run time, with kind invariant. soma check warns about a delete on such a slot under the code W0014 (habit_warning). Record a correction as a new entry instead, or drop [immutable] if entries must change.

When you see it

soma check reports this rule (kind immutable_write) as the warning W0014 habit_warning, never as E0089: the checker files every "habit" issue under W0014.